Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int (i)=0; (i)<(n); (i)++)

typedef pair<int,int> P;
int dx[] = {0,1,0,-1};
int dy[] = {1,0,-1,0};

int main(){
	int H,W;
	cin >> H >> W;
	vector<string> map(H);
	rep(i,H) cin >> map[i];

	queue<P> que;
	vector<vector<int>> d(H,vector<int>(W,-1));
	d[0][0] = 0;
	que.push(P(0,0));
	while(!que.empty()){
		P p = que.front(); que.pop();
		int x = p.first; int y = p.second;
		if(x==W-1 && y==H-1) break;
		rep(i,4){
			int nx = x + dx[i];
			int ny = y + dy[i];
			if(nx>=0 && nx<W && ny>=0 && ny<H && map[ny][nx]=='.' && d[ny][nx]==-1){
				que.push(P(nx,ny));
				d[ny][nx] = d[y][x] + 1;
			}
		}
	}

	int cnt=0;
	rep(i,H){ cnt += count(map[i].begin(), map[i].end(), '.'); }

	if(d[H-1][W-1]==-1){ cout << -1 << endl; }
	else { cout << cnt-d[H-1][W-1] -1  << endl; }

}